Sometimes it just happens. The store clerk forgets to remove the security device from the DVD, but no alarm sounds since the device was already deactivated at the register. The device locks you out of the case. With a few simple household tools, you can get into that case in no time.
Place the weaker magnet on the outside of the security device. This pulls a small metal piece located inside of the device flat against the outer portion of the lock, allowing you to slide it out by moving the magnet toward the open end of the device.
Push the plastic of the device inward toward the DVD case. This aligns a metal bar inside it with its opening. Sometimes it becomes stuck or out of place due to previous mishandling. Misalignment prevents the metal from being removed.
Place the stronger magnet on the outside of the device. Slide it along and toward the open end. This moves the metal bar outward. Pull the plastic portion of the device away from the DVD case as you are doing this. That allows the opening to widen for the removal of the metal bar.
Remove the plastic portion of the security device from the DVD case. It should simply fall off after the final metal piece is removed.
You will need a very strong magnet, like that used by a computer hard drive.